Timor-leste is located on the seafront, coastal communities take the water for their daily needs derived from seawater. It needs some treatment for sea water into fresh water. Water treatment selected is activated carbon from mangrove roots. Research method using carbonization and activation process. Activation using HCl dan H2SO4. The result areis the biggest worth of chloride levels decrease 15.3% using activated carbon mangrove roots with the activation of H2SO4.